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Title:
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BUCKBLADE: buckling load design methods for rotor blades
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Author(s):
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Published by:
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Publication date:
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ECN
Solar Energy
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1-5-1999
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ECN report number:
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Document type:
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ECN-C--99-015
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ECN publication
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Number of pages:
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Full text:
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17
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Download PDF
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Abstract:
In the JOULE-III project BUCKBLADE an investigation is performed into theapplicability of several buckling load prediction tools and methods to rotor
blade design. This investigation concerns the assessment of the relevant
aspects for buckling of rotor blades and consequently collect, describe and
validate a number of buckling load prediction methods. Based on several
design handbooks and publications a set of so-called 'Design rules' has been
formulated. Together with other buckling load predictions methods these
'Design rules' are validated for application to rotor blade design. Part of
this validation was based on experiments on two rotor blades that were built
and tested within the project. On each of these rotor blades two buckling
tests have been carried out. After analysing and comparing the first test
results, five parameter studies are performed. The most important conclusions
are: (1) For accurate buckling load predictions it is important to have
correct values of all orthotropic material properties. This requires tests on
batches of material that are made with the same manufacturing process as the
rotor blades; (2) All buckling load prediction tools are appropriate for long
flat- and curved orthotropic panels under compression. Some tools describe
sandwich structures and have shown to be appropriate for buckling load
predictions of symmetric sandwiches (sandwiches with equal facings); (3)
Omission of the longitudinal curvature and the pre-buckling deformation in
calculations for box-type structures under bending leads to an
over-estimation of 25% to 35%; (4) Geometric imperfections of the blade
structure leads to a reduction in buckling strength. For a geometric
imperfection with the shape of the collapse mode and an amplitude of 1% of
the wall thickness, the critical load is reduced with 3% to 6%. For sandwich
panels with thin facings local imperfections give a strong reduction of the
face-wrinkling-buckling load
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